Flow control valves are widely used in various flow control fields. For example, the flow control valve is used to control lubricant oil to lubricate a car engine system. One common flow control valve includes a valve body, a valve spool, a linear actuator and a restoring spring. The valve body includes an interior hollow chamber for receiving the valve spool. A sidewall of the valve body forms fluid ports to be in communication with the hollow chamber. Under the action of the linear actuator and the restoring spring, the valve spool is positioned at different locations to allow different fluid ports to be in communication with the hollow chamber, thereby controlling a flow direction of the fluid.
In general, in order to avoid unsmooth armature movement due to eccentricity between the valve spool and the armature of the linear actuator, the contact between the valve spool and the armature is required to have a high precision. In addition, in order to avoid leakage and achieve function of the valve, inner diameters of various portions of the valve are required to be precisely configured. These requirements bring great challenges to mass production and operation reliability of the valves.